1. Field of the Invention
The present invention relates generally to controlling characteristics of transconductance amplifiers.
2. Background Art
In transconductance amplifiers, switching resistance (e.g., degeneration impedance) is a characteristic circuit designers commonly seek to control through use of a number of different techniques. One traditional technique includes providing a transistor-based switch within the transconductance amplifier to control the degeneration impedance characteristics. Although this technique provides a level of control, its use produces several undesirable side-effects. For example, when changes in the degeneration impedance occur in a nonlinear fashion, or occur too quickly, glitches can occur in the output current of the amplifier.
Other traditional approaches to minimizing the effects of these glitches, as well as other instability problems, include the use of resistor capacitor (RC) delay circuits to retard the transition of the switch. The use of RC delay circuits is especially prevalent in low-noise applications, such as within programmable gain amplifiers.
The use of an RC delay circuits, however, requires large resistors and capacitors, which consumes integrated circuit (IC) board real estate. The RC circuits also require use of an extra pin on the IC.
Thus, although traditional techniques are available to minimize the occurrence of glitches and other instability factors in transconductance amplifiers, many of these techniques are costly and/or impractical.
What is needed, therefore, is a more practical approach to minimizing glitches in the output current of transconductance amplifiers caused by controlling the switching resistance. More specifically, what is needed is a method and system to programmably control the switching resistance in a transconductance amplifier. Also, what is needed is a system and method to control the speed at which the resistance switch is turned on and off, in order to further minimize glitches and other instability by-products.